Reinforcing yarns or cords

ABSTRACT

A METHOD FOR MAKING TEXTILE YARNS OR CORDS OF ENHANCED COMPRESSION MODULUS. A MULTIFILAMENT LOW-TWIST YARN IS COATED WITH A LIQUID WHICH CAN SUBSEQUENTLY BE CONVERTED TO AN ELASTIC SOLID HAVING A HIGH POISSON&#39;&#39;S RATIO, THE DEPTH OF PENETRATION OF THE LIQUID INTO THE LOW-TWIST YARN BEING AT LEAST SUFFICIENT TO BOND TOGETHER 30 PERCENT OF THE FILAMENTS COMPOSING THE YARN, CONVERTING THE LIQUID INTO THE ELASTIC SOLID TO FORM A YARN ACCORDING TO THE INVENTION OR TWISTING TWO OR MORE COATED YARNS TOGETHER AND CONVERTING THE LIQUID INTO THE ELASTIC SOLID TO FORM A CORD.

United States Patent 3,624,999 REINFORCING YARNS 0R CORDS Maurice A. Young, Lichfield, Statfordshire, England, as-

signor to The Dunlop Company Limited, London, England N0 Drawing. Filed July 28, 1969, Ser. No. 845,587 Claims priority, application Great Britain, Aug. 3, 1968, 37,147/ 68 Int. Cl. D02g 3/36, 3/40, 3/48 US. Cl. 57-153 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to reinforcing yarns and cords and particularly to yarns and cords for reinforcing dynamic rubber goods.

Textile yarns and cords intended for reinforcing dynamic rubber articles, such as tyres or conveyor belts, have sufficient twist inserted to enable them to withstand severe compressive strains under conditions of abuse. The insertion of twist lowers the strength of the textile reinforcement and also its modulus and for this reason the twist inserted is a compromise between strength and/or modulus and durability.

It is often desirable to have the highest attainable modulus or stilfness in particular types of high performance product, for example, under the tread of radial ply tyres and as a warp reinforcement on long-haul conveyor belts. This requirement has led to the use of small section steel cables in both these areas, though textiles are also used whenever possible because of their greater ease of handling. The moduli of some fibres such as fibreglass and high modulus rayon are adequate for high performance products provided that very low twist angles are used but this latter condition reduces the endurance potential of the fibres.

According to the present invention a reinforcing yarn comprises an encapsulated multifilament low-twist yarn in which the encapsulating material is an elastic solid having a high Poissons ratio and penetrates the whole of the yarn outer surface to a depth at least suflicient to bond together 30% of the filaments composing the yarn.

According to the present invention also a method for the manufacture of a reinforcing yarn comprises coating 8. multifilament low-twist yarn with a liquid which can subsequently be converted to an elastic solid having a high Poissons ratio, the depth of penetration into the multifilament yarn of the liquid being at least sufiicient to bond together 30% of the filaments composing the yarn, and converting said liquid to said elastic solid.

The multifilament low-twist yarn may be one of the usual textile materials, for example, rayon, nylon, polyester, poly(vinyl alcohol). By low-twist yarn in this specification is meant yarn having a twist factor of less than 0.036 where the twist factor of the yarn is the twist in turns per inch in the yarn divided by (Specific gravity X yarn denier) The liquid coating may be converted into the elastic solid in any of a number of ways, for example, cooling, chemical cross-linking, the actual method used being of 3,624,999 Patented Dec. 7, 1971 relatively minor importance and depending only on the liquid used.

The elastic solid must have a high Poissons ratio preferably at least 0.45 measured at tensile strains not greater than 5% and it is particularly preferred that the Poissons ratio of the elastic solid is at least 0.48 measured at tensile strains not greater than 5%.

Preferably the liquid is a Resorcinol-Formaldehyde- Latex (RFL) adhesive composition. Examples of suitable RFL Compositions are (a) an aqueous dispersion of resorcinol-formaldehyde resin, vinyl pyridine rubber, and butadiene rubber and (b) an aqueous dispersion of resorcinolformaldehyde resin and natural rubber.

Examples of other suitable liquids are solutions of polymers in organic solvents, for example, a solution of cis polyisoprene in n-hexane containing dicumyl peroxide, and liquid polymers, for example liquid polyurethanes.

The multifilament textile yarns may be used to make reinforcing cords. In this case the cords are preferably twisted after the liquid has been applied to the yarns but before the liquid has been converted to the elastic solid to avoid pre-stressing the encapsulating material.

The cord may be made in this way by coating and cordmaking simultaneously using an in-line or planetary cabling machine in which the liquid coating is applied to the yarns just prior to the yarns coming together to form the cord. This method results in a symmetrically shaped cord cross-section which is very easily handled.

Preferably, cords made from the encapsulated multifilament low-twist yarn have yarn helix angles of less than 19 measured with respect to the cord axis.

The encapsulated multifilament low-twist yarns of the present invention have enhanced resistance to compression compared with the untreated yarns. Thus cords made from the encapsulated yarns have a higher modulus than cords made from untreated yarn whilst retaining good durability.

An additional benefit of the encapsulation is that a degree of consolidation is given to the yarns making them easier to handle and making the producers twist unnecessary. The liquid coating is preferably applied to twistless yarns as soon as possible after production, rayon being particularly suitable for treatment since the speed at which it is spun is suitable for the extra stage of coating.

If desired, the multifilament low-twist yarns may be given an adhesive pro-treatment before encapsulation. Thus polyester multifilament yarns can be given a pretreatment of the blocked isocyanate type, nylon multifilament yarns can be given a similar pre-treatment and rayon multifilament yarns may be pre-treated by inclusion of a small proportion of resorcinol in the spin finish used in their production. Poly(vinyl alcohol) yarns may also be pre-treated particularly where zinc chloride or similar treatment has been used on the filaments to increase the modulus of the surface layers.

The invention is illustrated in the following examples:

Wet weight (gmS.)

Resorcinol 108 Formaldehyde (as a 37% w./v. aqueous solution 180 Gen-Tac Latex (40% by w. total solids) 1807 Pliolite 2104 latex (60% by w. total solids) 728 Water 1535 Sodium Hydroxide (as a 10% w./v. aqueous solution) 10 Inspection revealed that 50% to 70% of the filaments were bound together by the dried adhesive. Three such yarns were twisted together on a ring doubling textile machine to 1.5 turns per inch. The cords so formed were embedded in a rubber compound of vulcanised hardness 65 B8. and molded into a cylinder such that their axes were parallel to the axis of the cylinder. This cylinder was compressed on an Instron tester and a load-deflection graph obtained from which a value of compression modulus was calculated. By comparison with the compression modulus of an all rubber cylinder the component due to the cord was calculated. Similar measurements were made on cylinders containing a denier Terylene polyester cord partially encapsulated with an RFL composition of high rubber/resin ratio having a Poissons ratio of 0.46.

The Terylene yarn had been pretreated with a dilute polyvinyl acetate latex to aid adhesion to the RFL. Similar measurements were made for comparison purposes on rubber cylinders containing (1) a denier Courtaulds Tenasco super 140 rayon cord of 8.5 turns per inch twist conventionally treated with an RFL adhesive and (2) a brass coated steel tyre cord of 0.3 inch lay 6 x 3 x 0.0059" over 1 x 3 x 0.0059". The results revealed:

1 Denier.

Mean load Tan to buckle twist ends/ specimen Cord Construction angle inch (kgm.)

Encapsulated rayon 3/2,200 denler 0. 13 11 5. 0 Fibreglass G75-5/3 0. 12 ll 3. 7

The impregnation of rayon results in a cord of higher compression modulus than fibreglass.

EXAMPLE 4 Radial ply tyres were built in 175-13 size using breakers of the cord made as described in Example 2. These tyres were compared with standard production tyres.

Results of tests are shown below:

The effect of treating the yarns prior to cord forming with a rubbery adhesive has clearly boosted their compression modulus much nearer to that of steeel tyre cord.

EXAMPLE 2 Three yarns of Courtaulds Tenasco super 105 rayon and their producers twist removed on a ring twisting machine and were then cabled on a machine working on the planetary principle to an equal 2.5/2.5 turns per inch construction. The three yarns were brought together by passing them through a glass funnel mounted on the axis of the twisting head. A high rubber/resin ratio RFL adhesive of Poissons ratio 0.48 measured at a tensile strain of 5% was at the same time introduced into the funnel through a side arm so that the twistless yarns were almost completely impregnated with RFL before cord forming occurred.

The formulation of the RFL adhesive was as follows:

Wet weight (gms) 72 The cord was then passed through a chamber heated to 170 C. to dry and react the adhesive. Inspection by scanning electron microscope revealed almost complete encapsulation of the filaments by the rubbery composition.

EXAMPLE 3 Cords made by the technique described in Example 2 were wound on a frame and moulded into rubber so that a rubber pad was formed having parallel cord reinforcing Thus a tyre of equal stiffness and durability can be made with a lower textile content in the breaker by using the techniques of encapsulation.

Having now described my invention what I claim is:

1. A reinforcing yarn comprising an encapsulated multifilament low-twist yarn in which the encapsulating material is an elastic solid having a high Poissons ratio of at least 0.45 measured at tensile strains not greater than 5 percent and penetrating the whole of the yarn outer surface to a depth at least sufficient to bond together 30 percent of the filaments composing a yarn.

2. A yarn according to claim 1 in which the elastic solid is derived from a resorcinol-formaldehyde-latex adhesive composition.

3. A yarn according to claim 1 which is of rayon, nylon, polyester or poly(vinyl alcohol).

4. A yarn according to claim 3 in which the encapsulated low-twist yarn has been given an adhesive pretreatment before encapsulation.

5. A method for the manufacture of a reinforcing yarn which comprises coating a multifilament low-twist yarn with a liquid which can subsequently be converted to an elastic solid having a high 'Poissons ratio of at least 0.45 measured at tensile strains not greater than 5 percent, the depth of penetration into the multifilament yarn of the liquid being at least sufiicient to bond together 30 percent of the filaments composing the yarn and converting said liquid to said elastic solid.

6. A method according to claim 5 in which the liquid is a resorcinol-formaldehyde-latex adhesive composition.

7. A method according to claim 5 in which the lowtwist yarn is of rayon, nylon, polyester or poly(vinyl alcohol).

8. A reinforcing cord comprising at least two strands twisted together in which at least one of the strands is a reinforcing yarn as claimed in claim 1.

9. A method for the manufacture of a reinforcing cord which comprises coating at least two multifilament lowtwist yarns with a liquid which can subsequently be converted to an elastic solid having a high Poissons ratio, the depth of penetration into the multifilament yarn of the liquid being at least sufiicient to bond together 30 percent of the filaments composing the yarn, twisting the yarns together and subsequently converting the liquid into the elastic solid.

10. A method according to claim 9 in which the Poissons ratio of the elastic solid is at least 0.45 measured at tensile strains not greater than 5 percent.

11. A method according to claim 10 in which the lowtwist yarns are of rayon, nylon, polyester or poly(vinyl alcohol).

References Cited UNITED STATES PATENTS 2,691,614 10/1954 Wilson 57153 5 2,998,338 8/1961 Tung 57153 X 3,395,529 8/1968 Ray 57-140 C 3,410,749 11/1968 Chmiel 5714O C 3,458,989 8/1969 OBrien et a1. 571S3 10 JOHN PETRAKES,

Primary Examiner U.S. Cl. X.R. 

